Quad encoder problems

[Darrel Taylor]

Darn 40 posts per page.

Smitty, if you missed it, go back to post #40, page 1.
Steve and I both hit it at the same minute
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[smitty505000]

Crud! You guys are convincing me that this will not work. I didnt think the forces would be that bad. I guess it is like walking and carrying a glass of water, and we all know how it sloshes around.

Ok so a Parallax dual accelerometer shows where down is? Is it effected by inertia?

What about a pair of Mem's inclinometers from Digital ADIS16203?

I need to do some more reading I guess.

Smitty

[Darrel Taylor]

Is it effected by inertia?

Yes it is. That's why it can't give an artificial horizon.

What about a pair of Mem's inclinometers from Digital ADIS16203?

At $48 a piece for a single axis, It's makes the dual axis for $29.95 look a lot better.
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[smitty505000]

I am a little confused. Will inertia effect the ADIS16203 digital inclinometer as well? Dosnt it work off the earths magnetic field?

Is there any way I can make this artificial horizon work without a PHD in astrophysics?

Smitty

[sayzer]

....

Is there any way I can make this artificial horizon work without a PHD in astrophysics?
..

I was about the say that this issue is getting too complicated for me to follow.

[SteveB]

Here is a quote from the datasheet of the ADIS16203:

The ADIS16203 is a calibrated digital inclinometer that provides a full 360° of measurement range in any rotational plane that is parallel to the earth’s gravity. A dual-axis accelerometer provides the base-sensing function, which resolves the earth’s gravity into two orthogonal vectors, as displayed in Figure 23. A power-efficient approach to a common trigonometric identity converts these orthogonal vectors into an incline-angle measurement.

It is an accelerometer. Thus, in flight, will only be accurate when the plane is in wings level, unaccelerated flight. In other conditions, it will be giving you the resulting sum of all accelerations on the plane, which will certianly not be the same as the acceleration of the earth's gravity.

Steve

[sayzer]

Does that mean that if the speed in any direction is constant (meaning not increasing or decreasing) then you get zero?



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[Luciano]

Hi,

See these links.

Vibrating structure gyroscope

http://www.invensense.com/shared/pdf/MEMSGyroComp.pdf
http://www.analog.com/library/analog...37-03/gyro.pdf
http://www.nec-tokin.com/english/pro...ramicgyro.html
http://www.nec-tokinamerica.com/prod...ts/pd-057e.pdf

Best regards,

Luciano

[SteveB]

Does that mean that if the speed in any direction is constant (meaning not increasing or decreasing) then you get zero?

An aircraft can experiance both linear and angular acceleration in 3 axis (6 in total). If there is NO acceleration in any axis, the answer to your question is yes (and maybe no-see next paragraph). This is not "0 g". In this stabilized flight, the aircraft (and occupants) would experiance "1 g", just like what you feel sitting in front of your computer screen (unless you are really exicted playing the lastest and greatest video game )). Accelerometers would read "0", since no acceleration is occuring.

The main problem with accelerometers is that they will always be referenced to the aircraft itself. I can fly my airplane upside-down, and still make it "feel" to the accelerometer as if It was experiancing the same accelerations as level flight (but not for long). This makes them unable to provide useful attitude infomation.

A Gyro, on the otherhand, can be "spun-up" and aligned with the surface of the earth. The better the gyro, the longer it will remain aligned with it's initial reference. This will then provide the independent reference needed for attitude information.

Don't know if this helped, or just made the water muddier.

Steve